Constant-volume hydraulic shock-absorbers



Nov. 1, 1955 A. A. L. GIRARD I CONSTANT-VOLUME HYDRAULIC SHOCK-ABSORBERS 3 Sheets-Sheet 1 Filed Feb. 5, 1952 In vemor' Alexandre Au um: Loh Gl'rard After ey Nov. 1, 1955 A. A. L. GIRARD CONSTANT-VOLUME HYDRAULIC SHOCK-ABSORBERS Filed Feb. 5, 1952 3 Sheets-Sheet 5 fll xglmre Angus/2M G/rard In venfor 4/70/v7ey United Patent CONSTANT-VOLUME HYDRAULIC SHOCK-ABSORBERS Alexandre Auguste Lon Girard, Saint-Cloud, France Application February 5, 1952, Serial No. 270,018

Claims priority, application France February 23, 1951 4 Claims. (Cl. 188-89) Hydraulic shock-absorbers are known which comprise one. or a plurality of pressure chambers and one or a plurality of through-flow chambers, wherein the fraction or the whole of the liquid is caused to flow from one pressure chamber to another pressure chamber across one or a plurality of through=flow chambers.

Theoretically, these shock-absorbers are assumed to operate full of liquid, but as a matter of fact this is never the case since the liquid, irrespective of its nature, has a coefficient of expansion that differs substantially from that of the material constituting the casing containing it. As a consequence, it is necessary to provide an air pocket in the through-flow chamber in order to compensate the variations occurring in the expansion of the liquid. As a result, the liquid on its way from one pressure chamber to another contacts this air pocket and becomes loaded with air, that is, emulsified. This is a source of inconvenience in the operation of the shockabsorber, as commonly observed, in that before the positive retarding efiect occurs there is a zone of minor resistance in the stroke of the actuating lever, which is irnputable to the compression of emulsified oil.

It is the essential scope of the present invention to overcome this drawback in shock-absorbers operating according to the above-defined principle.

For this purpose, to the through-flow chamber of a constant-volume shock-absorber of the rotary or reciprocating vane type there is added an auxiliary chamber connected with the through-flow chamber by a one-way valve adapted to permit the passage of liquid only from the auxiliary chamber to the through-flow chamber, and by an orifice permanently connecting both these chambers, or by a spring-loaded valve permitting the passage of liquid only in the through-flow chamber-auxiliary chamber direction.

The accompanying drawings illustrate diagrammatically by way of example a few modes of embodiment of the invention the details of which will be described presently. In the drawings:

Figure 1 is a diagrammatical section through a first embodiment.

Figure 2 is a diagrammati'cal sectional view of a modified detail of the embodiment of Figure 1.

Figures 3 and 4 are an axial view and a cross-sectional view respectively of a further embodiment, and

Figure 5 is a sectional view of a modified detail.

Referring now to the drawings, Fig. 1 illustrates a known shock-absorber of the reciprocating piston type constructed as follows. It comprises a body 1 in which are slidably mounted a pair of coupled pistons 3, 4 rigidly interconnected through a rod 0. The body 1 is fixed to the unsprung portion of the vehicle and the pistons are connected with the sprung portion of the vehicle, or vice-versa. As a result, the coupled pistons 3, 4 are movable within the body 1 of the shock-absorber in the directions of the arrows U or V; each piston is provided with a one-way valve 5 and 6 respectively.

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Thus, the device comprises three main chambers X, Y, Z and grooves 7, 8 are formed in the inner wall of the body for the purpose set forth below.

This assembly operates as follows: When the pistons 3, 4 are moved in the direction of the arrow ,U the liquid is compressed in chamber X, valve 5 is closed and the liquid therein is forced into chamber Z through groove 7 and thence to chamber Y through valve 6. Similarly, when the pistons are moved in the direction of the arrow V the liquid compressed in chamber Y escapes through groove 8 into chamber Z and thence to chamber X across the valve 5. As already pointed out hereinabove the body 1 cannot be filled completely with liquid because the expansion of this liquid should be kept into account with respect to the body expansion. It is therefore necessary to provide an auxiliary chamber T which may conveniently be fitted at the upper portion of the device shown. This chamber T communicates with the chamber Z on the one hand through a port provided with a one-way valve 9 and on the other hand through an orifice 10.

This specific arrangement results from the following observation: it has been found that in a shock-absorber of this type, pulsations produced by the set of valves 5, 6 occur in the chamber Z. Besides, it will be seen that the scope of the one-way valve 9 is to prevent the liquid from flowing from chamber Z to chamber T.

However, it has been found that if the liquid expands for one reason or another, this valve 9 is seated while the still expanding liquid leaks through the shaft packing of the device. Hence the necessity of the orifice 10 through which the liquid may flow freely into the auxiliary chamber T.

As the liquid does not expand rapidly the crosssectional area of this orifice 10. may be very small compared with that of the one-way valve 9. As a result, during each stroke a small fraction of the liquid will flow from chamber Z to chamber T and then back to chamber Z through the port of valve 9, without contacting the air trapped in the upper portion of the auxiliary chamber T. Of course, the chamber T should be given an adequate volume so that the ports 9 and 10 shall in no circumstance contact the air trapped in this chamber T. Besides, the latter may be formed with bafiie means 11 or wire-gauze filters in order to prevent the liquid in chamber T from emulsifying with the air trapped therein due to the jolts of the vehicle on which the device, is mounted.

Fig. 2 is a modified form of embodiment wherein the port 10 is replaced with an orifice 12 provided with a one-way valve 13 adjusted for a given pressure. The operation is the same as in the preceding example except that on expanding the liquid opens the spring-loaded valve 1.3 for flowing from Z to T. Obviously, at this moment the pressure set up in chamber Z is proportional with the force of the valve spring.

Figs. 3 and 4 illustrate a hydraulic shock-absorber of the rotary-valve type comprising a cylindrical body 14 having a closed bottom 15. In the body 14 is rotatably mounted a shaft 16 carrying a pair of rigid vanes 17, 18 acting as diaphragm means in the cylindrical body.

The shaft 16 is controlled by a lever 19.

The body 14 is fixed to the sprung portion of the vehicle and the lever 19 is operatively connected to the unsprung portion thereof, or vice-verse.

The body 14 comprises in addition a fixed partition 20 fastened to the body by means of blind pins 21, thereby dividing the inner space of the body into three chambers X, Y, Z all filled with liquid. The apparatus is made.

leak-proof by a suitable shaft packing 22 the inner face 3 of which is connected through a port 23 with the chamber Z.

The vane 17 has mounted thereon a one-way automatic valve 24 whereby the liquid may flow across ports 26 from chamber Z to chamber Y but not in the opposite direction. The other vane 18 has mounted thereon a similar one-way valve so that the liquid may flow across ports 27 from chamber Z to chamber X but not in the opposite direction.

The bottom wall 15 is formed with a groove 28 the length of which matches approximately the amplitude of the circular stroke of the corresponding vane 18; another groove 29 cooperates with the other vane 17 and a third groove 30 interconnecting the chambers X and Y may be more or less obturated by means of a cock 31 adapted to be operated from the outside through a control lever 32. On top of this device is fixed (for instance by welding) a reservoir 33 closed by a lid 34. In the bottom of this reservoir is fitted a one-way valve consisting of a ball 35 so arranged as to allow liquid to flow from chamber T to chamber Z but not in the reverse direction. Besides, these chambers may communicate through a fine hole 38 bored in the valve seat 36. A screw plug 37 is provided for filling the device and indicating the average normal level of the liquid therein.

When the vanes are moved in the direction of the arrow U the liquid is compressed in chamber X and thus forced into chamber Z through channel 28 and also into chamber Y through channel 30. Finally, the liquid may flow from chamber Z to chamber Y across holes 26 and valve 24 open by the differential pressure produced.

If at that moment a pulsation occurs in chamber Z, a minimal fraction of the liquid will flow through orifice 38 into chamber T, but the resulting vacuum will be compensated immediately by the operation of the automatic one-way valve 35 and in no case the liquid passing through chamber Z will be mixed with air, that is, emulsified.

Similarly, when the vanes are moved in the direction of the arrow V, the liquid is compressed in chamber Y and flows through channel 29 into chamber Z while another portion of the liquid flows through channel 30 into chamber X. The liquid having escaped into chamber Z will subsequently pass into chamber X across holes 27 and valve 25 open by the ditferential pressure built up.

The operation of the ball valve 35 and the orifice 38 cooperating therewith is the same as in the arrangement illustrated in Figs. 1 and 2 and described hereabove.

Thus, if on account of a rise in temperature the liquid expands, it may freely occupy the additional room oflfered by the chamber T through the orifice 38 and conversely, when the liquid contracts, it passes through both orifice 38 and automatic valve 35.

Fig. 5 illustrates a modified embodiment of this device. In fact, it comprises like the preceding example an automatic one-way valve 39 permitting the liquid to flow from T to Z. The seat 40 is another valve that permits the liquid to flow from Z to T only and is loaded by a light spring 41.

The ball valve 39 operates like the valve 35 described above. Besides, the expanding liquid unseats the valve 40 in order to pass from chamber Z into chamber T. If it contracts, it flows from chamber T into chamber Z by depressing the ball valve 39.

The object of the spring 41 is to enable the valve 40 to withstand any pulsations occurring during the operation of the device; therefore, it should be adjusted accordingly.

What I claim is:

1. A hydraulic shock-absorber for damping the oscillations of two assemblies oscillating in relation to each other, comprising a casing adapted to move bodily with one of said oscillating assemblies, a rigid system adapted to move bodily with the other oscillating assembly and comprising a pair of vanes adapted to perform sliding oscillations in said casing and defining in said casing a pair of compression chambers and an intermediate chamber, each vane having a through orifice connecting said intermediate chamber with one of said compression chambers, grooves in said casing which constitute narrow passages between each compression chamber and said intermediate chamber, a filling chamber having a bottom wall overlying said intermediate chamber, said bottom wall comprising a pair of passages connecting said filling chamber with said intermediate chamber, a liquid filling completely said compression and intermediate chambers and partially said filling chamber, a one-way valve mounted in each of said vanes for preventing said liquid from escaping from one compression chamber through the relevant vane orifice, means adapted to prevent said liquid from flowing back to said filling chamber through one of said passages in the bottom wall of said filling chamber, and means adapted to prevent said liquid from flowing back in the same direction through the other passage of said bottom wall of said filling chamber.

2. A hydraulic shock-absorber for damping the oscillations of two assemblies oscillating in relation to each other, comprising a casing adapted to move bodily with one of said oscillating assemblies, a rigid system adapted to move bodily with the other oscillating assembly and comprising a pair of vanes mounted for efiecting sliding oscillations in said casing and defining in said casing two compression chambers and an intermediate chamber, each vane having a through orifice connecting said intermediate chamber with one of said compression chambers, grooves in said casing which constitute narrow passages between each compression chamber and said intermediate chamber, a filling chamber having a bottom wall overlying said intermediate chamber, and baffle means provided above said bottom wall from a certain level upwards, said bottom wall having formed therethrough two passages connecting said filling chamber with said intermediate chamber, a liquid filling completely said compression and intermediate chambers and partially said filling chamber up to a level higher than that from which said baflie means are provided, a one-way valve mounted in each Vane for preventing said liquid from escaping from a compression chamber through said vane orifice, means adapted to prevent said liquid from flowing back to said filling chamber through one of said passages in the bottom wall of said filling chamber, and means adapted to prevent said liquid from flowing back in the same direction through the other passage of said bottom wall of said filling chamber.

3. A hydraulic shock-absorber for damping the oscillations of two assemblies oscillating in relation to each other, comprising a casing adapted to move bodily with one of said oscillating assemblies, a rigid system adapted to move bodily with the other oscillating assembly and comprising a pair of vanes mounted for effecting sliding oscillations in said casing and defining in said casing two compression chambers and an intermediate chamber, each vane having a through orifice connecting said intermediate chamber with one of said compression chambers, grooves in said casing which constitute narrow passages between each compression chamber and said intermediate chamber, a filling chamber having a bottom wall overlying said intermediate chamber, said bottom wall having formed therethrough two passages connecting said filling chamber with said intermediate chamber, a liquid filling completely said compression and intermediate chambers and partially said filling chamber, a one-way valve mounted in each vane and adapted to prevent said liquid from escaping through said vane orifice from said compression chambers, another oneway valve adapted to prevent said liquid from flowing back to said filling chamber through one of said passages in said bottom wall, and a spring-loaded valve for preventing said liquid from flowing back through the other passage when the liquid pressure exerted on said last-mentioned valve is lower than a predetermined value.

4. A hydraulic shock-absorber adapted to damp out the oscillations of two assemblies oscillating with respect to each other, comprising a casing adapted to move bodily with one of said oscillating assemblies, a rigid system adapted to move bodily With the other oscillating assemblies and comprising two vanes mounted for efiecting sliding oscillations in said casing and defining in said casing two compression chambers and an intermediate chamber, each vane having a through orifice connecting said intermediate chamber with one of said compression chambers, and grooves formed in said casing to constitute narrow passages between each compression chamber and said intermediate chamber, a filling chamber having a bottom wall overlying said intermediate chamber, a passage between one of said main chambers and said filling chamber, a movable valve seat mounted in the bottom wall of said filling chamber and facing said intermediate chamber, an axial aperture in said valve seat which constitutes one passage between said filling chamber and said intermediate chamber, a check valve in the axial aperture of said valve seat, said valve seat having a valve-shaped peripheral contour bearing on said bottom of said filling chamber and uncovering about said peripheral contour an annular port when said seat is lifted above said bottom wall, said annular port constituting another passage between said filling chamber and said intermediate chamber, a liquid filling completely said compression and intermediate chambers, and partially said filling chamber, a one-way valve mounted in each of said vanes to prevent said liquid from escaping from a compression chamber through said orifice of the vane mounted under said valve seat, thereby preventing said liquid from flowing back to said filling chamber through said axial aperture in said valve seat, and a spring disposed vertically in said filling chamber and urging said valve seat against said bottom wall of said filling chamber while preventing said annular port from being opened as long as the pressure exerted by said liquid on said valve seat is below a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 611,486 Jackson Sept. 27, 1898 1,946,525 Eickhofi et al Feb. 13, 1934 2,014,162 Benedek et a1 Sept. 10, 1935 2,036,955 Padgett Apr. 7, 1936 2,054,467 Peo Sept. 15, 1936 2,070,409 Mitchell Feb. 9, 1937 2,314,493 Guy Mar. 23, 1943 2,341,096 Haywood Feb. 8, 194 2,653,683 Strauss Sept. 29, 1953 FOREIGN PATENTS 425,881 France June 22, 1911 

